INTRACELLULAR PH REGULATION IN ISCHEMIC MYOCARDIUM

缺血心肌细胞内 PH 值调节

• 批准号: 2028950
• 负责人: JOANNE S INGWALL
• 金额: $ 19.21万
• 依托单位: BRIGHAM AND WOMEN'S HOSPITAL
• 依托单位国家: 美国
• 财政年份: 1997
• 资助国家: 美国
• 起止时间: 1997-02-01 至 2000-01-31
• 项目状态: 已结题
• 来源: https://reporter.nih.gov/project-details/2028950
• 关键词: 5' nucleotidase; acidity /alkalinity; adenine nucleotides; adenosine monophosphate; adenosine triphosphate; enzyme activity; heart function; intracellular transport; isolation perfusion; laboratory rat; myocardial ischemia /hypoxia; myocardium; nuclear magnetic resonance spectroscopy; nucleotide metabolism

DESCRIPTION (adapted from the applicant's abstract): By combining results from 31P NMR spectroscopy of the rat heart and conventional analysis of freeze-clamped tissue the applicant has obtained evidence for a regulatory role for intracellular pH (pHi) on adenine nucleotide resynthesis in myocardium improved by ischemia. Specifically, by combining high-flow hypoxia (where pHi does not fall below 7.0) and ischemia (where pH falls to 6), the applicant found that low pHi leads to greater accumulation of AMP during ischemia and to greater ATP resynthesis and improved functional recovery during reflow. Following 28 minutes of global normothermic ischemia, the amount of ATP synthesized upon reperfusion equals the amount of AMP that had accumulated during ischemia. Essentially all of the ATP resynthesized during reperfusion is via this mechanism. The applicant hypothesizes that the underlying mechanism for this observation is inhibition of cytoplasmic AMP-specific 5'-nucleotidase (5'-NT) by H+, thereby, preventing the conversion of AMP to adenosine. If this is the case, low pHi protects the myocardium by preserving a significant fraction of the cytosolic adenine nucleotide pool during ischemia. Using NMR spectroscopy of isolated perfused rat heart and conventional biochemical tools, the applicant will pursue three specific aims which focus on the consequences of acidic pH on the capacity of the ischemic myocardium to synthesize ATP during reperfusion: (1) to define in vivo regulation of 5'-NT activity; (2) to determine the time course of activation, inhibition and reactivation of 5'-NT activity; (3) to define the relationship among pHi, ATP and return of cardiac function.

描述(改编自申请人的摘要)：结合结果 从大鼠心脏的31P核磁共振波谱和常规分析 冷冻夹住的组织申请人已获得监管机构的证据 细胞内pH(Phi)对腺嘌呤核苷酸再合成的影响 心肌缺血后改善。具体地说，通过结合高流量 缺氧(phi不低于7.0)和缺血(phi降至 6)，申请人发现低phi会导致更大的AMP积累 在缺血期间和更大的ATP再合成和改善的功能 回流过程中的恢复。在全球常温28分钟后 缺血，再灌流时合成的三磷酸腺苷的量等于 在缺血过程中积聚的AMP。基本上所有的ATP 再灌流期间的再合成就是通过这一机制实现的。申请人 假设这一观察的潜在机制是 H+对胞质AMP特异性5‘-核苷酸酶(5’-NT)的抑制作用 从而阻止AMP转化为腺苷。如果这是 在这种情况下，低phi通过保留很大一部分心肌来保护心肌 缺血时胞浆腺嘌呤核苷酸池的变化。使用核磁共振 大鼠离体心灌流光谱与常规生化 工具，申请者将追求三个具体目标，重点是 酸性pH对缺血心肌细胞功能的影响 再灌流中合成三磷酸腺苷：(1)确定在体调控 5‘-NT活性；(2)测定激活、抑制的时间进程 和5‘-NT活性的重新激活；(3)确定 PHI、ATP与心功能恢复